Preposterous and Unreasonable

Preposterous

Preposterous adjective - Showing or marked by a lack of good sense or judgment.
Usage example: a preposterous suggestion to go swimming in this freezing weather

Unreasonable is a synonym for preposterous in absurd topic. In some cases you can use "Unreasonable" instead an adjective "Preposterous", when it comes to topics like ridiculous, usual. popular alternative

Unreasonable

Unreasonable adjective - Having no basis in reason or fact.
Usage example: an unreasonable assumption

Preposterous is a synonym for unreasonable in usual topic. You can use "Preposterous" instead an adjective "Unreasonable", if it concerns topics such as absurd, unacceptable, not logical or sensible. popular alternative

Cite this Source
Unreasonable and Preposterous. (2016). Retrieved 2026, July 21, from https://thesaurus.plus/related/preposterous/unreasonable
Preposterous & Unreasonable. N.p., 2016. Web. 21 Jul. 2026. <https://thesaurus.plus/related/preposterous/unreasonable>.
Unreasonable or Preposterous. 2016. Accessed July 21, 2026. https://thesaurus.plus/related/preposterous/unreasonable.
Google Ngram Viewer shows how "preposterous" and "unreasonable" have occurred on timeline